A cascade-functionalized ZnCdS/Ce-MOF composite gate coupled with a self-replicating catalytic hairpin assembly for...

A high-performance organic photoelectrochemical transistor (OPECT) sensor was successfully constructed based on a ZnCdS/Ce-MOF composite gate integrated with a self-replicating catalytic hairpin assembly (SRCHA) signal-amplification strategy, which enables ultrasensitive and highly selective detection of the pesticide imidacloprid. The sensor employs visible-light-responsive ZnCdS and peroxidase-mimetic Ce-MOF to form a composite endowed with cascading light-harvesting and enzyme-like functionality as the gate photoelectric material. Under illumination, the ZnCdS/Ce-MOF composite generates a significantly enhanced photogenerated voltage, which effectively modulates the channel current of PEDOT:PSS. In the presence of the target, this system triggers a SRCHA cascade amplification reaction, producing a large number of long DNA chains loaded with gold nanoparticles (Au NPs). Subsequently, the Au NPs catalyze the oxidation of glucose to produce H₂O₂, which is then converted in situ by Ce-MOF into hydroxyl radicals that selectively etch ZnCdS in the composite. This etching process reduces the photoelectric conversion efficiency of the gate and causes attenuation of the channel current signal. The fabricated OPECT sensor demonstrates excellent performance, with a linear detection range for imidacloprid from 500 fg mL^-1 to 500 ng mL^-1 and a low detection limit of 44.78 fg mL^-1 (S/N = 3). It also exhibits good selectivity, stability, and reproducibility. This study provides a cascade-functionalized ZnCdS/Ce-MOF composite gate integrated with a self-replicating catalytic hairpin assembly for OPECT sensing of imidacloprid, and delineates a novel material and signal-amplification strategy for ultrasensitive pesticide detection in complex matrices.